Loved by over 2.2 million students

Over 90%
improved by at least one letter grade.

OneClass has been such a huge help in my studies at UofT especially since I am a transfer student. OneClass is the study buddy I never had before and definitely gives me the extra push to get from a B to an A!

Leah — University of Toronto

Balancing social life With academics can be difficult, that is why I'm so glad that OneClass is out there where I can find the top notes for all of my classes. Now I can be the all-star student I want to be.

Saarim — University of Michigan

As a college student living on a college budget, I love how easy it is to earn gift cards just by submitting my notes.

Jenna — University of Wisconsin

OneClass has allowed me to catch up with my most difficult course! #lifesaver

Anne — University of California

Description

Lecture 26:
Thermoregulation:
• Temperature effects many processes and enzymes inside the body such as the rate of enzymatic
reactions and cell membrane fluidity (cholesterol).
o At low temperature the membrane is rigid and less permeable
o At high temperature the membrane is too fluid
• There is a thermal limit for animal life and it changes between animals
o Tb is different between ectotherms and endotherms
o Ectotherms: are animals that can’t produce energy inside their body and rely on
external sources of animals to maintain their internal energy.
o Endotherms: are animals that produce energy inside their body to maintain their
internal temperature compared to the environmental changes.
• Body heat= heat produced + (heat gained – heat lost)= metabolic heat + heat transferred with
environment
• Heat is transferred from the environment to the body by 5 ways:
• 1)conduction: direct contact between a cool object and warmer body would lead to the transfer
of energy from the warmer to the cooler
• 2) radiation: transfer of heat from a warmer object to a cooler object through electromagnetic
waves (light), no direct contact is needed
• 3) convention: transfer of heat from warmer to cooler objects by air currents where the warmer
air rises and is replaced by cooler air
• 4) evaporation: conversion of liquid to gas; sweat to vapor; the heat of vaporization is absorbed
from the skin
• 5) heat storage: has 3 factors:
o A) surface area: the smaller the animal the faster it’s capable of loosing or gaining
energy from the environment. Also the metabolic rate is higher in smaller animals
compared to the larger animals
o B) Temperature gradient: the larger the temperature difference between the organism
and its environment the greater the heat transfer due to a greater temperature
gradient.
o C) specific heat conductance: the specific heat conductance is a constant value for
different types of objects that determines how much heat would be transferred. The
larger the specific heat the more energy would be transferred and thus lost. Animals
with high specific heat tend to have body temperatures that fluctuates with the ambient
environment. The lower the specific heat conductance constant the better the
organism is in insulating its body temperature and its known as insulation (fur and fat)
• ΔHtotal= ΔHmetabolism + ΔHconduction/convention + ΔH radiation + ΔHevaporation+
ΔHstorage
• Mechanisms for regulating heat transfer:
o 1) behavioral changes: moving into another environment that favors the optimal
temperature
o 2) internal physiological adjustments: changes in blood flow or sweating that is
controlled by the autonomic nervous system (sympathetic NS) o 3) morphological changes: changes in the pelage or insulation of the body.
• The temperature classification of animals is based on:
• 1) body temperatures:
o A) poikilotherms: body temperature changes as the environment temperature changes
o B) homeotherms: body temperature is maintained compared to the changed
environment where they are active in both cold and warm
• Source of stored heat in the body:
o A) ectotherms: body heat is captured from the environment
o B) endotherms: body heat is produced in the body
o C) heterotherms: some endothermic heat production but they don’t always regulate
their body temperatures within a narrow range
ECTOTHERMS:
• They obtain heat from external environment
• They do not produce enough metabolic energy or heat
• They rely on conductance for capturing heat from the environment
• They have a specific range or preferred body temperatures
• They are poorly insulated and regulate their body temperatures through behavioral changes
• In cold environments:
o Since the heat in the environment at this level is low, and the temperatures are freezing;
the organism is at a high risk of ice crystal formation inside the cell that would rupture
the cell and destroy them.
o The organism is made up of water 70%
o Three different strategies are taken into consideration to prevent intracellular ice
formation:
o 1) freeze tolerance: ice is formed through out the body as in frogs, but it’s not formed
inside the cells